Technical Field
The present invention relates to a wiring substrate and a method for manufacturing the same, and a semiconductor package.
Related Art
There is known a wiring substrate having a core layer provided with an insulating base material and plural linear conductors penetrating from one surface to the other surface of the insulating base material, in which a wiring layer is formed on both surfaces of the core layer. In this wiring substrate, the wiring layers which are disposed in a position facing each other across the core layer are electrically connected to each other by the linear conductors in the core layer. In addition, the wiring layer formed on each of the both surfaces of the core layer is covered by an insulating layer.    [Patent Document 1] Japanese Patent Application Publication No. 2011-171531A
However, since the above-described wiring substrate is provided with the linear conductors over the entirety of the insulating base material, in a portion where the wiring layer does not exist, an upper end surface and an lower end surface of the linear conductor are exposed in a position approximately flush with the one surface and the other surface of the insulating base material, respectively. The linear conductor exposing in a portion where the wiring layer does not exist electrically float, and the end surfaces are exposed, and therefore, there was involved such a problem that insulation reliability between the wiring layers is lowered.
In addition, there is proposed a wiring substrate in which in the entirety of one surface and the other surface of an insulating base material, an upper end surface and a lower end surface of a linear conductor are depressed relative to the one surface and the other surface of the insulating base material, respectively to form concaves and convexes, and an insulating layer is filled in the concave and convex portions. In this wiring substrate, since the upper end surface and the lower end surface of the linear conductor are exposed in a position more depressed than the one surface and the other surface of the insulating base material, respectively, its insulating reliability is enhanced as compared with the above-described wiring substrate. However, since the wiring layer is formed in the concave and convex portions of the core layer, there was involved such a problem that connection reliability between the wiring layer and the linear conductor is lowered.